Questions tagged [ideal-gas]

A gas that behaves as randomly moving, non-interacting molecules. This allows a simplified equation of state.

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Why does entropy of an ideal gas break the third law of thermodynamics? [duplicate]

I was recently looking at the entropy equation for an ideal gas, show below $$S=NR\left\{\frac{5}{2}+\ln\left[\frac{V}{N}\left(\frac{2\pi mRT}{h^2}\right)^{3/2}\right]\right\}$$ And what troubles me ...
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Does thermal equilibration affect compression work for an ideal gas?

Consider compression of an ideal gas that is uniform in pressure but nonuniform in temperature, from volume $V_1$ to $V_2$. For simplicity of the problem let's say the gas is divided into 2 regions $A$...
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Partition Function of an Ideal Gas

Which is the correct partition function for an ideal (bosonic) gas at high $T$: 1) Sum over the number of particles in each momentum state: $$ z_{\vec{p}} = 1 + e^{- \varepsilon_{\vec{p}}/T} + ... = ...
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What happens to pressure when a liquid turns into a gas in a confined chamber?

I'm doing an experiment requiring immense pressures. Since I do not have access to a pump that can create these pressures I settled on something different... Instead of using a pump I want to utilize ...
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How long does it take a gas to equilibrate with a container's temperature?

Initial Conditions in a vessel: P~my unknown, but ~100torr, V=5000cc, T=35C, gas is 50/50 N2/He Laser drill a hole in the initial volume of diameter=10mils through a chamber wall thickness of 0.75mm. ...
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What happens when a photon hits a particle (radiative heat transfer, photoelectric effect)?

By relating temperature to particle motion, the kinetic theory of gases gives an intuitive explanation of conductive heat transfer; faster particles collide with slower ones to transfer kinetic energy....
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Assumptions and limitations for ideal gas

Assumption: In the assumption for ideal gas law, it is stated:"The time it takes to collide is negligible compared with the time between collisions." For, this assumption, can i just say there is only ...
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Determining Gas Constant $R$ from Boyles Law?

I have done an experiment (Boyles Law experiment using Boyles Law Apparatus) in order to determine the value of the gas constant $R$. I have also taken into account the dead space volume in my ...
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Insert sensors in an aerostat with helium?

Hy is possible for you insert sensors (to calculate pressure and temperature) inside an aerostat with helium ? I ask this because... I have an helium balloon anchored to the ground by a rope with a ...
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Is the Ideal gas approximation still valid if I have sizeable dynamic pressure

Say, if I have a hose blowing or sucking air into/outo a bigger compartment, can I still regard the static preassure as obeying ideal gas law?
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How to calculate the specific weight of air?

First of all sorry for my bad English ... I have to calculate the specific weight of air knowing that in the air there is actually a small percentage of water vapor. Therefore the specific weight of ...
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Why use a cube as a reference volume in the kinetic theory of gases?

In basic kinetic theory we often use cubes. For example, the derivation of the ideal gas law is done with a cubical volume. Is a cube necessary for it to work? If not, wouldn't a sphere be more ...
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64 views

Work done on a gas enclosed in a container

According to everywhere work done on system of a gas is equal to $p\,\mathrm dV$ but here $p$ is just the external pressure. Shouldn't internal forces be considered while calculating work done thus ...
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Derivation of density of states for a gas with $N$ states

I am trying to find any information on the derivation of the density of states for a system with periodic boundary conditions in 3D. I know how it works with 1 particle since I have seen the ...
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Does $PV\propto T$ apply to a photon gas?

For an ultrarelativistic ideal gas, I know that $p=\frac{u}3$; $TV^3 =$ constant; $pV\propto T$. For a photon gas, I know that the first two results apply as well. However, I am unsure if the third ...
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Bouyancy of ozone gas

If ozone is $O_3$ why is it an outer layer of the atmosphere? It seems $O_3$ would sink in a solution of $O_2$, rather than float on it.
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Ideal gas as balls in boxes in different ensembles

I have some questions about the ideal gas in different ensembles. Often boxes with moving balls are used to explain an ensemble. Now I am confused what the difference would be in the corresponding ...
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Applying ideal gas law to every day problems

Three classical examples of seeing the ideal gas law in action: crumpled water bottle in cold car crumpled water bottle after your flight lands fridge door harder to open a second time after first. ...
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Boltzmann transport equation for granular gases

I am researching about granular gases and their collisions, and have come across this Boltzmann transport equation: $$\frac { \partial f ( v ) } { \partial t } = \iint d u _ { 1 } d u _ { 2 } f \left( ...
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Deriving pressure from particle velocity: missing 1/3 factor

Let us assume we have a perfect gas, isotropic, homogeneous, inside a cube of side a. We want to calculate the pressure as a function of the velocities of the particles inside. We must find the ...
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What is the criteria of trapped ideal gas to form Bose-Einstein condensate (BEC)?

If we have ideal gas of bosons in a trapped harmonic potential, is the only necessary thing for BEC is a temperature less than the transition temperature? Or is there any other things we should keep ...
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Compression of gas [closed]

What happens when a gas kept in a metallic container is suddenly compressed via a piston and left for some time? Does the pressure increase or decrease?
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How was Maxwell able to derive velocity distribution? [closed]

Did he assume that their velocities follow some kind of statistical distribution and fit the parameters accordingly. Or did he mathematically prove it?
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Thermodynamic Entropy seems to be contradictory

For an ideal gas the entropy change with energy is inversely proportional to temperature: This must yield: $$S=\frac 3 2 k_B \ N ln(T)$$ For various reasons, this equation is hard to find. ...
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Does quantum gases obey ideal gas equation $ PV= nRT$?

At extremely low temperature, does an ideal gas of bosons or fermions obey the ideal gas equation, $PV= nRT$?
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Are forces of gases intensive or extensive?

What am I wrong at in here: I read that pressure is an intensive property. According to this and to $P=\frac{nRT}{V}$, can this be true: $(1)$: When $V$ is constant, increasing $n$ won't increase $P$,...
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Definition of volume of a gas and Amagat's law

How would you define the volume of an (ideal) gas? I would say it is the volume of the container holding the gas (whether it is a fixed container or a flexible one like a balloon). However, ...
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How to find Volumetric Expansion if not given the volumetric coefficient?

I'm doing a few practice questions on thermodynamics to prepare for my exams next year and I have been stuck with this question ever since. I tried to move on to answer other questions and came back ...
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Proportionality between pressure, volume, and number of microstates for an ideal gas?

I'm pretty new to Thermodynamics, but I've been playing around with some different computations to reinforce my understanding. I came across the result $$\Omega \propto \left( PV^\gamma \right)^{fN/2},...
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What would be the total pressure in this container in accordance to the Ideal Gas Law?

If I had an apparatus such as the one below: where each of the four blue lines represents a valve, and then I was to open the three lower valves such that the pipes connecting the three containers ...
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Does the amount/speed a balloon rises vary with the temperature of the gas inside, given a constant type and amount of gas?

I'm attempting to conduct an experiment with a balloon. I fill it up with some amount of helium. If I cool the balloon down (say with liquid nitrogen), the balloon's volume will decrease (because of ...
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Joule expansion and center of mass

This question comes from a doubt resulting from some physics forums. Similar to and related to this question, I have a doubt on Joule expansion raised by reading too much bad faith arguments. I'm not ...
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Does Avogadro's law only apply to ideal gases?

I know the ideal gas law may change a little when for real gases or diatomic ones does Avogadro's law change too or does it stay the same?
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Limitations of converting pressure into kinetic energy

Bernoulli's principle states that an increase in the kinetic energy of a fluid occurs simultaneously with a decrease in pressure for isentropic processes. What then limits us from converting all of ...
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Ideal gas and moveable pistons

Suppose there is an ideal, monatomic gas contained in a cylinder with a moveable piston and you bring that system (system = gas only) through some process. If that process changes the volume (or ...
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How does a gas spring work?

I read Wikipedia and do not understand the following. If you create pressure on the gas (or any spring) it gives pressure against. Why is the gas spring holding mass when pulled out, and while ...
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What kind of ideal gas process a positively sloped line in a $pV$-diagram represents?

I've come across an ideal gas process which can be represented by a positively sloped line in the $pV$ diagram. I found something about this on KhanAcademy, but it's simply a worked example on how to ...
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Finding the internal energy change of an ideal monoatomic gas using a graph

Here's what the text says (in the graph, $V$ is in cubic meters and $P$ is in atm): A sample of an ideal monoatomic gas goes trough the process shown in the figure below. From $A$ to $B$, the ...
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Modelling Oxygen Diffusion [closed]

I am creating a system of differential equations to model oxygen diffusion in tissue. I have: $\frac{dP}{dt}=D_o\nabla^2P-qn$ where $q$ represents the sink rate at positions occupied by cells, $n$ ...
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Kelvin and kinetic theory of gases

I know that the degree of freedom increase by 2 when the temperature is high and decrease by 2 when the temperature is low. A dumb question here, what temperature is considered as 'high temperature' ...
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Energy Equation of an ideal gas in expanding space-time

Short question: If the energy equation of an ideal plasma is written as follows: $\begin{equation} \frac{\mathrm{d}p}{\mathrm{d}t}=-\Gamma p\nabla\cdot v-\left(\Gamma-1\right)\left( \nabla\cdot q-\...
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How does an ideal gas radiate?

Recently I've been reading a lot about blackbody radiation, Rayleigh-Jeans law, Planck's law and the UV catastrophe. In deriving the Rayleigh-Jeans and Planck's laws, we are examining a perfectly ...
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Carnot cycle with isometric processes

Consider the following slightly modified Carnot cycle with two extra isochoric processes for an ideal gas of adiabatic constant $\gamma$ working between temperatures $T_H>T_C$. A pV diagram is ...
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What would happen to a room full of neutrons?

Suppose you had a room full of neutrons at standard pressure and temperature. Would it be just like a room full of hydrogen?
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Combined gas equation in adiabatic process

We know that $PV^{\gamma}=constant $. There are also 2 more equations which relates $P$ & $T$ and $V$ & $R$. Is there any equation which relates all these 3 things like ideal gas equation? ...
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Weird and unintuitive results from thermodynamics/hydrostatics for an isothermal atmosphere and possible explanation(?)

It is known from hydrostatics that for a fluid in equilibrium in a gravitational field, $$\frac{dP}{dz} = -ρg$$ Let us from now on suppose the atmosphere is isothermal and has temperature $T$. We ...
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49 views

Is it possible to estimate the average time until entropy decreases a certain amount?

We all know the classical Joule free expansion experiment for an ideal gas: we trap an ideal gas inside half of a cylinder. Then, we open the door and the gas expands to the whole cylinder. After ...
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What is the meaning of $PV^\gamma=$ constant in an adiabatic process?

In an adiabatic process, heat transfer doesn't occur and hence $\Delta U=-W$ (an increase in internal energy due to work done on the system or a decrease in internal energy due to work done on the ...
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Difficulty in calculating effusion rate using the kinetic theory of gases and statistical mechanics

I have tried multiple sources and methods, but my attempts at a proof of the number of particles leaving a gas using statistical mechanics keep finding the same wrong result. I have tried to read ...
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Confusion while deriving kinetic-molecular theory of gases

How many of the molecules will collide within a given area A of the wall normal to the x-direction in some fixed time interval Δt ? On average half the molecules have a positive x-...